It all depends on the number of points you need, the inventory of the room category you want, the popularity of that time of year (from what I understand, the fall is a prime DVC reservation time, due to the Epcot Food and Wine festival), and of course, whether a member with the right points/home resort happens to have listed with David's at the time your reservation request is pending. However, our history with David's has been largely successful:
- Fall 2014 visit (moderate crowd week, mid-October): 5-night rental, 2-BR villa at Wilderness Lodge: Made request to David's at 11 months. No immediate members with the points, but we joined their virtual queue and got our reservation through David's about 3 weeks later.
- Fall 2016 visit (moderate crowd week, 2 weeks before Thanksgiving): wanted a 6-night rental for a value studio at Animal Kingdom Lodge. Made request to David's at 11 months. No members with the needed points, and availability for those studios (there are only a handful of them) was gone within a few weeks. David's notified us of this so we didn't wait around needlessly any further. They offered us alternatives (OKW and SS), but we opted to forego renting DVC points altogether and book a standard room in a moderate instead: that deal ended up being sweeter, as free dining was ultimately offered during our stay. I suspect that if we'd been willing to upgrade our reservation request to a different room category at AKL with a higher inventory and a higher point cost (e.g., standard studio, savannah view...) we'd have been able to get a reservation, but we weren't ready to make that leap.
- Upcoming Spring 2018 visit (moderate crowd week, 3 weeks after Easter): wanted a split stay: 3 nights in a studio at Beach Club, followed by 2 nights in a studio at the Polynesian. Made both requests to David's at 11 months (2 requests, each made 11 months from the respective arrival dates for each resort). No immediate members with the points, so we joined the virtual queue. David's got us the Beach Club reservation within 7 days, and the Polynesian reservation 8 days, after the 11-month mark.